Gas sensor chamber and odor detection method

ABSTRACT

The invention relates to a chamber ( 2 ) for gas sensors ( 9 ) to be used in a device ( 1 ) for detecting aromas or odors. The chamber ( 2 ) comprises three portions ( 5, 6, 7 ) in which there is a uniform, turbulence-free flow (F) of gas or vapors to be analyzed, and at least one gas sensor ( 9 ) positioned in the central portion in such a way as to be immersed in and to laterally and tangentially interact with the flow (F). The chamber ( 2 ) also comprises a heating and temperature regulating device ( 16, 17 ). The invention also relates to an odor detection method which comprises a step in which a uniform, turbulence-free flow (F) of gas or vapor interacts with a gas sensor ( 9 ) laterally and tangentially.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a gas sensor chamber and an odordetection method that uses the chamber according to the invention.

[0002] One non-limiting example of an application of the chamberaccording to the invention is in apparatus for detecting aromas or odorsproduced by food products. This specification expressly refers to usesof this kind but without thereby restricting the scope of the invention.

[0003] Apparatus for detecting the aromas or odors produced by foodproducts is used to check the quality of a food product not only interms of the constancy of its properties during the preparation processbut also to detect aging or spoiling.

[0004] This type of check is very useful because it provides informationquickly without having to come into contact with the product to bechecked.

[0005] Devices are known which detect aromas or odors using artificialsensors that work in a manner similar to the olfactory system ofmammals.

[0006] Chemical resistors are one example of sensors of this kind. Thistype of sensor is made from special materials that absorb the gas/vaporto be detected and produce a change in electrical resistance.

[0007] The substance absorbed by the sensor material produces a changein the resistance to the passage of current through an electricalcircuit to which the sensor is connected.

[0008] Usually, the sensors used for olfactory measurement analysis aretransducers which convert an interaction with defined gaseous substancesinto electrical signals.

[0009] Each sensor is differently sensitive to a specific group ofgaseous substances and therefore, to produce an “odor print”, that is tosay, a specific aroma or odor, with satisfactory precision, severalolfactory sensors are required, each differently sensitive to thatspecific group of gaseous substances.

[0010] Further, once the sensors used to identify gas mixtures havegenerated a certain signal, they must be cleared of the gas they haveabsorbed before they can proceed to carrying out another analysis.

[0011] It follows that the arrangement of the sensors and the shape ofthe chamber in which the sensors are located are very important factorsfor the correct identification of the odor or aroma.

[0012] One gas sensor arrangement is known from U.S. Pat. No.6,516,653-B2.

[0013] That document describes an apparatus device comprising one ormore gas or vapor sensors located in a room where concentrations ormixtures of gases or vapors have to be monitored, and with a diffusionbody placed in front of the sensors.

[0014] According to the invention described in that document, the gassensors, whose responsiveness is influenced by the design of thecontainer enclosing the space to be monitored, by contamination or bystatic conditions in the space to be monitored, are positioned in a ductwhere a flow that accelerates the diffusion of the gases or vapors to beanalyzed is generated, thus increasing the responsiveness of the gassensors.

SUMMARY OF THE INVENTION

[0015] One aim of the present invention is to provide an improved gassensor chamber permitting optimum operation of the gas sensors.

[0016] Another aim of the present invention is to provide a gas sensorchamber housing one or more sensors in such a way that all the sensorsare in the same detection conditions.

[0017] A further aim of the present invention is to provide a gas sensorchamber permitting rapid detection of the signals produced by thegaseous substances and fast resetting of the sensors so they are readyto carry out the next analysis.

[0018] According to one aspect of it, the present invention provides agas sensor chamber as defined in claim 1.

[0019] Yet another aim of the present invention is to provide animproved method for detecting odors in which a uniform flow of the gasesor vapors to be analyzed is made to interact laterally and tangentiallywith the gas sensors.

[0020] According to another aspect of it, the present invention providesa gas detection method as defined in claim 18.

[0021] The dependent claims describe preferred, advantageous embodimentsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The preferred embodiments of the invention will now be described,without restricting the scope of the inventive concept, with referenceto the accompanying drawings in which:

[0023]FIG. 1 is an axonometric view of an odor detection device equippedwith a gas sensor chamber made according to the present invention;

[0024]FIG. 2 is a schematic section view of the gas sensor chamber madeaccording to the present invention;

[0025]FIG. 3 is a schematic axonometric view of the gas sensor chamberillustrated in the figures listed above;

[0026]FIG. 4 is a schematic section view of another embodiment of thegas sensor chamber according to the present invention;

[0027]FIG. 5 is an axonometric view of a constructional form of the gassensor chamber according to the present invention; and

[0028]FIG. 6 is a longitudinal section view of the gas sensor chamberillustrated in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] With reference to the accompanying drawings, the odor detectiondevice equipped with the gas sensor chamber according to the inventionis denoted in its entirety by the numeral 1.

[0030] The device 1 essentially comprises a gas sensor chamber 2 and adiverter valve 3 with two connections a first connection to a zone inwhich the product to be checked is located and a second connection to aneutral reference gas—and a pump 4 to suck the reference gas or the airfrom the zone where the product to be checked is located.

[0031] The diverter valve 3 and the suction pump 4 do not form part ofthe subject-matter of the present invention and, for this reason, areillustrated schematically in FIG. 1.

[0032] As shown in the drawings, the chamber 2 comprises an inlet 2 aand an outlet 2 b for the flow F of gas or vapor to be analyzed, adivergent portion 5, a central sensor mounting portion 6 and aconvergent portion 7.

[0033] The central portion 6 has a total internal height H and presentsa lateral surface 6 a, of width L, on which there is at least one hole 8with a respective gas sensor 9 fitted in it. The sensor 9 has asensitive surface 10 located inside the central portion 6 in such a wayas to interact tangentially with the flow F of gas or vapors to beanalyzed. More specifically, as illustrated in FIG. 2, the sensitivesurface 10 is located approximately a third of the way up or down thetotal height H of the central portion 6.

[0034] The central portion 6 has an elongate, rectangular shaped crosssection so as to maximize the ratio of the area of the lateral surface 6a to the internal volume.

[0035] According to a preferred embodiment of the invention, the centralportion 6 houses six gas sensors 9 arranged in groups of three along thetop and bottom of the long sides of the lateral surface 6 a in adirection transversal to the flow F of gas or vapors to be analyzed.

[0036] As mentioned above, the sensitive surfaces 10 of the sensors 9 atthe top are located about a third of the way down the total height H ofthe central portion 6, whilst the surfaces 10 of the sensors 9 at thebottom are located about a third of the way up the total height H of thecentral portion 6.

[0037] In this way, the sensitive surfaces 10 of the sensors 9 allinteract with the flow F in the same way and without interfering witheach other. Since each sensor 9 is differently sensitive to a specificodorous mixture, this arrangement makes it possible to identify the odorprint in a precise and repeatable manner.

[0038] The elongate flattened shape of the central portion 6, with aheight H that is relatively small compared to its width L, isadvantageous for rapid detection of the odor or aroma because itminimizes the volume or gas or vapor to be analyzed relative to the sizeof the sensitive surfaces 10 of the sensors 9, thus allowing a highconcentration of odor or aroma inside the chamber 2.

[0039] The ratio of the width L to the height H (L/H) of the centralportion 6 may be between 8 and 12 and is preferably 9.

[0040] The sensitive surface 10 of each sensors 9 since it is inside thecentral portion 6 approximately a third of the way along the heightH—interacts in optimum manner with the flow F of the gas or vapor and isnot disturbed by the lateral surface 6 a of the central portion 6.

[0041] In the preferred embodiment, there are six sensors. This is apurely exemplary number and is a compromise between the need toprecisely identify the odor print and the cost and size of the odordetection device in its entirety.

[0042] It will therefore be understood that sensor chambers 2 accordingto the invention can be made with a larger or smaller number of sensorswithout departing from the scope of the inventive concept as defined inthe claims.

[0043] As illustrated in FIG. 5, each sensor 9 is fixed to the centralportion 6 by a plate 11 and screws, and also has a seal 12, such as anO-ring, to prevent infiltration of air from the outside environment. Theholes 8 in which the sensors 9 are fitted are shape or size coded sothat each sensor has a fixed position in the chamber 2 and cannot bechanged round with any of the others. For example, the holes 8 may havea different diameter and/or geometrical shape, matching the diameterand/or shape of the couplings on the respective sensors 9.

[0044] The divergent portion 5 connects the inlet 2 a, which is normallycircular, with the central portion 6, which has an elongate crosssection.

[0045] The divergent portion 5 must also create a flow of gas or vaporthat is as uniform and free of turbulence as possible.

[0046] To achieve this, the divergent portion 5 has a flattened conicalshape with an angle a of less than 12 degrees at the vertex of the cone.Larger angles α—around 50 degrees—are also possible but, in this case, adiffuser or uniformizer 13 must be fitted to correctly address orredirect the gas flow.

[0047] As a result, the cone angle α of the divergent portion 5 may fallwithin either of two possible ranges: angle α from 0 to 12 degreeswithout diffuser or uniformizer 13, or angle α from 40 to 65 degreeswith diffuser or uniformizer 13.

[0048] In a preferred embodiment with diffuser or uniformizer, the coneangle α is 52 degrees.

[0049] The flow diffuser or uniformizer 13 may be made from finemetallic mesh which straightens and uniformizes the passage of the flowF into the central portion 6.

[0050] The flow diffuser 13 presents an open area between 30 and 40%with a mesh size of between 300 and 500 μm (microns). In a preferredembodiment, the open area is 35% and the mesh size 380 μm (microns).

[0051] Alternatively, porous polymer membranes may be used, even onescapable of filtering out specific gaseous substances.

[0052] The novel feature of this chamber is the way in which the gas orvapor flow F interacts with the sensors 9, namely, laterally andtangentially, enabling the sensors 9 to work better.

[0053] That is because the interaction between the sensors 9 and thegases analyzed occurs through a reaction on the surface of the sensors 9and, consequently, tangential flow maximizes the responsiveness of thesensors 9.

[0054]FIG. 4 illustrates an embodiment of the chamber 2 where thelateral surface 6 a has smooth, rounded corners and edges all the wayaround it.

[0055] The convergent portion 7 may be made with the same geometricalcharacteristics as the divergent portion 5, which means that the twoportions 5 and 7 may be identical, with obvious advantages in terms ofproduction cost.

[0056] The portions 5, 7 may also have housings 14, 15 for othersensors, such as, for example, sensors to detect temperature andrelative humidity in the chamber 2.

[0057] In fact, it should be remembered that for optimum operation, thesensors 9 may need to be heated and that, since the temperature andrelative humidity in the chamber 2 affect the precision of odordetection, it is necessary to know and, if possible, control and modifythese conditions in the chamber 2. To maintain uniform detectionconditions, the chamber 2 may have heat insulation and the divergent andconvergent portions 5, 7 may be equipped with heaters 16, 17 attached tosaid portions 5, 7.

[0058] The heaters 16, 17 thus constitute a device for heating andregulating the temperature of the chamber 2 and may be based on embeddedresistors or cartridges.

[0059] The materials from which the chamber 2 is made must have goodproperties of inertia and resistance to absorption of aromas and odorsso as not to affect detection by the sensors 9. They must also have agood resistance to relatively high temperatures.

[0060] That is because certain types of sensors 9 must be heated totemperatures of around 300-500 degrees Celsius to work efficiently. Thechamber 2 may thus need to be heated by the heaters 16, 17 totemperatures around 50-80 degrees Celsius.

[0061] For these reasons, the chamber 2 may be made, for example, fromstainless steel, type AISI 304, and the seals between the differentparts of the chamber 2 may be made from polytetrafluoroethylene, usuallyknown as Teflon, a registered trademark of the Du Pont company.

[0062] The invention also concerns an odor detection method comprisingthe following steps:

[0063] sucking in the gas or vapor to be analyzed from the area wherethe product is located;

[0064] generating a uniform turbulence-free flow F of gas or vapor intoa sensor mounting portion 6;

[0065] making the flow F of gas or vapor interact laterally andtangentially with sensors 9;

[0066] collecting the signals generated by the sensors 9 and processingthem to define the odor print of the gas or vapor to be analyzed;

[0067] sucking in a neutral reference gas;

[0068] generating a uniform turbulence-free flow F of the neutralreference gas into the sensor mounting portion 6;

[0069] making the flow F of reference gas interact laterally andtangentially with the sensors 9 so as to clear the previously analyzedgas or vapor from the sensors 9 and make the sensors 9 ready to carryout another analysis.

[0070] The odor detection method also comprises steps of measuringtemperature and of controlling the temperature by heating the sensors 9and the chamber 2.

[0071] The invention has important advantages.

[0072] The chamber according to the invention is made in such a way thatall the sensors 9 interact simultaneously with the same flow of gas orvapor to be analyzed, the flow, in all cases, varying very little fromsensor to sensor.

[0073] The chamber according to the invention is shaped to permit quickand easy clearing after each analysis carried out.

[0074] The volume of the gas or vapor sample to be analyzed is reducedin relation to the geometrical and constructional constraints due to thesensors, pipe fittings and electrical connectors.

[0075] Chamber design is such that each sensor has a single,well-defined and easily identifiable mounting position.

[0076] The heat insulation, made to the measure of the chamber 2, andthe embedded resistor or cartridge heating system create constantlyoptimum conditions for detection.

[0077] The compact shape of the chamber 2 can be reduced in size withoutaltering its geometry and leaving unchanged the advantages describedabove.

[0078] The invention as described above may be modified and adapted inseveral ways without thereby departing from the scope of the inventiveconcept as defined in the claims.

[0079] Moreover, all the details of the invention may be substituted bytechnically equivalent elements.

What is claimed is
 1. A chamber (2) for gas sensors (9) in a device (1)for detecting aromas or odors, the device (1) including a container inwhich there is a flow (F) of gas or vapors to be analyzed, the chamber(2) comprising: an inlet (2 a) through which the flow (F) flows in; anoutlet (2 b) through which the flow (F) flows out; at least one gassensor (9) having a sensitive surface (10) positioned in such a way asto be immersed in and to laterally interact with the flow (F); wherebythe at least one sensor (9) detects a signal usable to identify the kindof gas or vapor to be analyzed.
 2. The chamber (2) for gas sensors (9)according to claim 1, wherein the sensitive surface (10) of each gassensor (9) is positioned in such a way as to laterally and tangentiallyinteract with the flow (F).
 3. The chamber (2) for gas sensors (9)according to claim 1, further comprising a central portion (6) having atotal internal height (H) and a lateral surface (6 a), of width L, onwhich there is at least one hole (8) with a respective gas sensor (9)fitted in it.
 4. The chamber (2) for gas sensors (9) according to claim3, wherein the central portion (6) has a width (L) to height (H) ratio(L/H) between 8 and
 12. 5. The chamber (2) for gas sensors (9) accordingto claim 3, wherein the central portion (6) has a width (L) to height(H) ratio (L/H) equal to
 9. 6. A chamber (2) for gas sensors (9) in adevice (1) for detecting aromas or odors, the device (1) including acontainer in which there is a flow (F) of gas or vapors to be analyzed,the chamber (2) comprising: an inlet (2 a) through which the flow (F)flows in; an outlet (2 b) through which the flow (F) flows out; acentral portion (6) having a total internal height (H) and a lateralsurface (6 a), of width L, on which there is at least one hole (8); atleast one gas sensor (9) having a sensitive surface (10) positioned inthe at least one hole (8) in such a way as to be immersed in and tolaterally interact with the flow (F); whereby the at least one sensor(9) detects a signal usable to identify the kind of gas or vapor to beanalyzed.
 7. The chamber (2) for gas sensors (9) according to claim 6,wherein the sensitive surface (10) of the sensor (9) is positionedapproximately a third of the way along the height (H) of the centralportion (6).
 8. The chamber (2) for gas sensors (9) according to claim6, further comprising a divergent portion (5) having a flattened conicalshape with an angle (α) at the vertex of the cone, the portion (5)connecting the inlet (2 a) to the central portion (6).
 9. The chamber(2) for gas sensors (9) according to claim 8, wherein the divergentportion (5) has a cone angle (α) between 0 and 12 degrees.
 10. Thechamber (2) for gas sensors (9) according to claim 6, furthercomprising: a divergent portion (5) having a flattened conical shapewith an angle (α) between 40 and 65 degrees at the vertex of the cone,the portion (5) connecting the inlet (2 a) to the central portion (6);and a diffuser or uniformizer (13) located between the divergent portion(5) and the central portion (6).
 11. The chamber (2) for gas sensors (9)according to claim 10, wherein the divergent portion (5) has a coneangle (α) equal to 52 degrees.
 12. The chamber (2) for gas sensors (9)according to claim 10, further comprising a convergent portion (7)having a flattened conical shape, the convergent portion (7) connectingthe central portion (6) to the outlet (2 b).
 13. The chamber (2) for gassensors (9) according to claim 12, wherein the convergent portion (7) issubstantially equal to the divergent portion (5).
 14. The chamber (2)for gas sensors (9) according to claim 10, further comprising a heatingand temperature regulating device (16, 17).
 15. The chamber (2) for gassensors (9) according to claim 10, wherein the diffuser or uniformizer(13) is made from fine metallic mesh which straightens and uniformizesthe passage of the flow (F) into the central portion (6).
 16. Thechamber (2) for gas sensors (9) according to claim 10, wherein the flowdiffuser or uniformizer (13) has an open area between 30 and 40% and amesh size between 300 and 500 μm (microns).
 17. The chamber (2) for gassensors (9) according to claim 10, wherein the flow diffuser oruniformizer (13) has an open area of 35% and a mesh size of 380 μm(microns).
 18. The chamber (2) for gas sensors (9) according to claim10, wherein the flow diffuser or uniformizer (13) is made from porouspolymer membranes.
 19. The chamber (2) for gas sensors (9) according toclaim 10, wherein the flow diffuser or uniformizer (13) is made fromporous polymer membranes having selective filtering properties inrelation to specific gaseous substances.
 20. A chamber (2) for gassensors (9) in a device (1) for detecting aromas or odors, the device(1) including a container in which there is a flow (F) of gas or vaporsto be analyzed, the chamber (2) comprising: an inlet (2 a) through whichthe flow (F) flows in; an outlet (2 b) through which the flow (F) flowsout; a central portion (6) having a total internal height (H) and alateral surface (6 a), of width L, on which there is at least one hole(8); a divergent portion (5) having a flattened conical shape with anangle (α) at the vertex of the cone, the portion (5) connecting theinlet (2 a) to the central portion (6); at least one gas sensor (9)having a sensitive surface (10) positioned in the at least one hole (8)in such a way as to be immersed in and to laterally interact with theflow (F); whereby the at least one sensor (9) detects a signal usable toidentify the kind of gas or vapor to be analyzed.
 21. The chamber (2)for gas sensors (9) according to claim 20, wherein the divergent portion(5) has a cone angle (α) between 0 and 12 degrees.
 22. The chamber (2)for gas sensors (9) according to claim 20, wherein the divergent portion(5) has a cone angle (α) between 40 and 65 degrees and the chamber (2)further comprises a diffuser or uniformizer (13) located between thedivergent portion (5) and the central portion (6).
 23. The chamber (2)for gas sensors (9) according to claim 22, wherein the divergent portion(5) has a cone angle (α) equal to 52 degrees.
 24. The chamber (2) forgas sensors (9) according to claim 20, further comprising a diffuser oruniformizer (13) located between the divergent portion (5) and thecentral portion (6).
 25. The chamber (2) for gas sensors (9) accordingto claim 20, wherein the diffuser or uniformizer (13) is made from finemetallic mesh which straightens and uniformizes the passage of the flow(F) into the central portion (6).
 26. The chamber (2) for gas sensors(9) according to claim 20, wherein the flow diffuser or uniformizer (13)has an open area between 30 and 40% and a mesh size between 300 and 500μm (microns).
 27. The chamber (2) for gas sensors (9) according to claim20, wherein the flow diffuser or uniformizer (13) has an open area of35% and a mesh size of 380 μm (microns).
 28. The chamber (2) for gassensors (9) according to claim 20, wherein the flow diffuser oruniformizer (13) is made from porous polymer membranes.
 29. The chamber(2) for gas sensors (9) according to claim 20, wherein the flow diffuseror uniformizer (13) is made from porous polymer membranes havingselective filtering properties in relation to specific gaseoussubstances.
 30. The chamber (2) for gas sensors (9) according to claim20, further comprising a convergent portion (7) having a flattenedconical shape, the convergent portion (7) connecting the central portion(6) to the outlet (2 b).
 31. The chamber (2) for gas sensors (9)according to claim 30, wherein the convergent portion (7) issubstantially equal to the divergent portion (5).
 32. The chamber (2)for gas sensors (9) according to claim 20, further comprising a heatingand temperature regulating device (16, 17).
 33. A chamber (2) for gassensors (9) in a device (1) for detecting aromas or odors, the device(1) including a container in which there is a flow (F) of gas or vaporsto be analyzed, the chamber (2) comprising: an inlet (2 a) through whichthe flow (F) flows in; an outlet (2 b) through which the flow (F) flowsout; a central portion (6) having a total internal height (H) and alateral surface (6 a), of width L, on which there is at least one hole(8); a divergent portion (5) having a flattened conical shape with anangle (α) at the vertex of the cone, the portion (5) connecting theinlet (2 a) to the central portion (6); a convergent portion (7) havinga flattened conical shape, the convergent portion (7) connecting thecentral portion (6) to the outlet (2 b); at least one gas sensor (9)having a sensitive surface (10) positioned in the at least one hole (8)in such a way as to be immersed in and to laterally interact with theflow (F); whereby the at least one sensor (9) detects a signal usable toidentify the kind of gas or vapor to be analyzed.
 34. The chamber (2)for gas sensors (9) according to claim 33, wherein the divergent portion(5) has a cone angle (α) between 0 and 12 degrees.
 35. The chamber (2)for gas sensors (9) according to claim 33, wherein the divergent portion(5) has a cone angle (α) between 40 and 65 degrees and the chamber (2)further comprises a diffuser or uniformizer (13) located between thedivergent portion (5) and the central portion (6).
 36. The chamber (2)for gas sensors (9) according to claim 35, wherein the divergent portion(5) has a cone angle (α) equal to 52 degrees.
 37. The chamber (2) forgas sensors (9) according to claim 33, wherein the convergent portion(5) has a cone angle between 0 and 12 degrees.
 38. The chamber (2) forgas sensors (9) according to claim 33, wherein the convergent portion(5) has a cone angle between 40 and 65 degrees.
 39. The chamber (2) forgas sensors (9) according to claim 33, wherein the convergent portion(5) has a cone angle equal to 52 degrees.
 40. The chamber (2) for gassensors (9) according to claim 33, wherein the convergent portion (7) issubstantially equal to the divergent portion (5).
 41. The chamber (2)for gas sensors (9) according to claim 33, further comprising a heatingand temperature regulating device (16, 17).
 42. An odor detection methodcomprising the following steps: sucking in the gas or vapor to beanalyzed from the area where the product to be checked is located;generating a uniform turbulence-free flow (F) of gas or vapor into asensor mounting portion (6); making the flow (F) of gas or vaporinteract laterally and tangentially with at least one sensor (9);collecting the signals generated by the sensor or sensors (9) andprocessing them to define the odor print of the gas or vapor to beanalyzed; sucking in a neutral reference gas; generating a uniformturbulence-free flow (F) of the neutral reference gas into the sensormounting portion (6); making the flow (F) of reference gas interactlaterally and tangentially with the sensor or sensors (9) so as to clearthe previously analyzed gas or vapor from the sensor or sensors (9) andmake the sensor or sensors (9) ready to carry out the next analysis. 43.The odor detection method according to claim 42, comprising a step ofmeasuring the temperature and of controlling the temperature by heatingthe chamber (2).
 44. The odor detection method according to claim 42,comprising a step of measuring the relative humidity and a step ofcontrolling the humidity by pre-treating the flow of gas or vaporintroduced into the chamber (2).